In this study, La–Mn–Cr perovskite-type catalysts were synthesized as LaMnO3,LaCrO3, and LaMn0.5Cr0.5O3 by a microwave-assisted gel-combustion method. They were then calcined at 600oC for 5h in air. X-ray diffraction (XRD) analysis indicated that the crystalline perovskite phase is the dominant phase formed in all the synthesized samples. The scanning electron microscopy (SEM) analysis showed that the perovskites have a full spongy and porous structure. The specific surface area (BET) analysis showed a specific surface area of about 12.4-26.8 m2/g, and the highest specific surface area belonged to the LaMn0.5Cr0.5O3 perovskite. Moreover, the highest oxygen mobility revealed by the temperature-programmed desorption of oxygen (O2–TPD) analysis was related to the LaMn0.5Cr0.5O3 sample. The catalytic activity of the synthesized perovskites in catalytic oxidation of 1000 ppm trichloroethylene (TCE) in air was investigated at different temperatures. The substituted perovskite (LaMn0.5Cr0.5O3) with the highest BET specific surface area and the highest oxygen mobility yielded the best catalytic performance among the probed perovskites.
In this work, the fast remediation of tert-butyl mercaptan from the polluted soil via a bimetallic Fenton treatment that included Fe2+/Fe3+/Fe0/Cu2+ in the presence of gasoline was studied. The analysis of variance and the Pareto analysis resulting from the central composite design (CCD) showed that the H2O2, CuSO4, Fe3O4 nanoparticles, nano zerovalent iron (nZVI), and gasoline initial concentrations as a secondary contaminant were influential factors on the removal efficiency of tert-butyl mercaptan (with an effectiveness of 2.09%, 13.38%, 1.92%, 2.01%, and 39.73% respectively). Moreover, the interaction of H2O2/nZVI, H2O2/nFe3O4, H2O2/CuSO4, nZVI/nFe3O4, and nZVI/CuSO4 had a positive effect on removal efficiency, while nFe3O4/CuSO4 had a negative one. Surprisingly, the mixing of nZVI and nFe3O4 before adding them to the reactor did not affect the removal efficiency. The optimum conditions suggested for the maximum removal efficiency of tert-butyl mercaptan were the minimum levels of the initial gasoline concentration (2.5 %w/w), a maximum level of CuSO4 (0.12 %w/w), and an optimum concentration of H2O2, nano-ZVI, and nano-Fe3O4 (8.92 %w/v, 0.1194 %w/w and 0.0898 %w/w, respectively) in the studied intervals. This condition led to a 99.27% efficiency removal of tert-butyl mercaptan removal in 20 minutes without pH and temperature adjustments.
Desulfurization-hydrogenation of thiophene and benzothiophene in hexadecane as a model diesel fuel was studied through a divided cell with the incorporation of the membrane electrode assembly (MEA) under different current density at a constant charge. The reduction of thiophenic compounds was investigated using prepared MoS2 nano-electrocatalyst and Nafion (commercial proton exchange membrane) and synthesized sulfonated poly ether ether ketone, SPEEK. The MoS2 electrocatalyst was characterized by field emission scanning electron microscopy and X-ray diffraction, which confirmed the formation of ball-like nano-thread of MoS2 with the size of 23-25 nm. Also, the electrocatalyst and/or MEA was electrochemically analyzed by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. The gas chromatography-mass spectroscopy analysis of reactants and products revealed the direct desulfurization on thiophene reduction process and desulfurization along with desulfurization pathway on benzothiophene reduction experiment. Maximum desulfurization efficiency of 79.6% at 20 mA cm-2 and 51.5% at 30 mA cm-2 under the constant charge of 300 C was obtained for thiophene using MoS2-Nafion and MoS2-SPEEK system respectively. Moreover, maximum hydrogenation and desulfurization efficiency of 28% and 59.1% occurred at 50 mA cm-2 and 70 mA cm-2 respectively for Benzohiophene-Nafion system under the constant charge of 400 C. distribution of products affirmed the more contribution of desulfurization reaction at higher current density against the hydrogenation process at lower current density.